FEEDING LACTATING MARES (H38-0300CM)
Cindy McCall, Ph.D.
Horse Extension Specialist

Nutritional demands of pregnancy require that mares have increased levels of nutrients to produce a healthy, vigorous foal. However, the nutritional requirements of mares increase most dramatically immediately after foaling. The lactating mare must recover from any stress involved in foaling, produce milk and rebreed within a short period of time after foaling. These activities require a high level of energy, protein and minerals in the mare’s diet. A 1200 pound mare will produce 2 to 3% of her body weight as milk daily during the first 3 months of lactation. Underfeeding mares during this period can result in decreased milk production, poor weight gains in the foal and weight loss in the mare.
A lactating mare needs 65% more protein and 44% more energy than during her last month of pregnancy. Calcium and phosphorus demands increase 55% and 28%, respectively, over her prefoaling needs. A lactating mare usually requires 2 to 3% of her body weight in feed (both forage and grain) daily. Accordingly, a 1200 pound lactating mare needs 24 to 36 pounds of feed daily. As with all horses, good quality hay or pasture should be the basis of the lactating mare’s diet, and some of her increased nutritional demands can be met with good quality pasture. However, the majority of lactating mares will need supplemental grain to meet their nutritional requirements.
Mares in early lactation require 1.1 Mcal of energy per pound of total feed. If they are consuming forage which provides a good source of energy, the mare can be fed less of the concentrate ration to meet her energy needs than if the forage is low in energy. One option to increase the energy content of the mare’s diet is to feed a diet that is high in fat. Many feed manufacturers market a high fat broodmare ration or a fat pellet that can be added to the horse’s feed. An alternative is to top dress the concentrate feed with vegetable oil. Feeding 5 to 10% of the concentrate ration in the form of fat allows horsemen to decrease the amount of grains fed to the horse while still providing the energy that the lactating mare needs. Because some heavily milking mares may need high levels of concentrates in their diet, the addition of fat and the subsequent reduction in concentrates may reduce the possibility of colic and founder in these mares.
The total diet of the mare during the first 90 days of lactation should contain at least 12% crude protein. If the mare is consuming forages with a high protein content, such as ryegrass, small grain pastures or legumes, a 10% crude protein concentrate should provide adequate protein to meet her total dietary needs. Mares consuming forages providing lower protein levels (generally orchardgrass, timothy, bahiagrass and bermudagrass) will need a concentrate feed with a higher protein content (generally around 16% crude protein) to meet their protein needs.
Additional calcium and phosphorus required by the mare during the first 90 days of lactation usually are met by adding minerals to the concentrate ration. Balanced feeds formulated for lactating mares and fed at normal amounts should provide enough minerals. However, providing trace mineralized salt free choice is a good management practice. There are several supplements available that provide a combination of protein, minerals and vitamins in a concentrated formula. Managers who cannot purchase a balanced concentrate ration formulated for lactating mares or who are lucky enough to have mares which stay in good body condition on only forage may utilize these supplements to ensure that broodmares are receiving adequate protein and minerals. However, adding these supplements to a balanced concentrate ration may result in excessive nutrients in the mare’s diet. In most cases these excessive nutrients will not harm the horse but are a waste of the producer’s money.
Lactating mares should have access to clean, fresh, cool water at all times. During hot environmental conditions, a lactating mare on dry feedstuffs may consume 25 gallons of water daily.
The increase in feed over that needed during pregnancy should be made gradually over a one to two week period to prevent colic and founder. Feeding the concentrate ration in at least two equal feedings allows mares to consume the amount of concentrates they need without overwhelming the digestive tract. Providing individual feeders for mares fed as a group can help the manager ensure that each mare is getting enough feed and can reduce injuries associated with feeding horses in troughs. Always put out more feeders than horses, scatter the feeders randomly and quickly dispense the feed so that all horses can start eating at approximately the same time. Group mares according to feed intake when possible to help control the amount of feed they consume.
By the fourth month of lactation, the mare’s daily nutrient requirements start to decline. Although milk volume remains fairly high, the energy content of the milk drops and the mare requires less of the concentrate ration than during early lactation. Omitting the mare’s concentrate ration during weaning helps decrease milk production by reducing the energy content of the mare’s diet. After weaning the foal, the mare again can be managed as a pregnant mare in early gestation. During this time her nutritional requirements are similar to a mature, idle horse. Free choice high quality roughage, water and trace mineralized salt will usually provide enough nutrients if the mare was in good body condition at weaning. If the mare was thin at weaning time or free choice roughage is not available a supplemental concentrate ration may be needed to restore her to a good body condition.